Dot matrix printing using thermal printheads is well known. Alphanumeric or other characters are formed by selectively heating small portions of thermally sensitive paper as the paper moves across the printhead surface. Resistors deposited in one or more rows along the length of the printing edge of the printheads are heated when power is applied. This heat marks thermally sensitive paper drawn across the printhead surface.
The resolution of thermal printing is generally limited by the density of the resistors on the printhead surface, which in turn is limited by the density of the electrodes and conductive paths leading to the resistors. As a general rule, electrodes, and therefore resistors, must be spaced equal to their width. Multiple-row spacing of resistive elements has increased the limit of print resolution; however, resolutions as great as 300 dots/inch have been difficult to produce economically. In general, very high resolution printheads are complex and expensive to construct.